mptcp: fix active subflow finalization

Active subflow are inserted into the connection list at creation time.
When the MPJ handshake completes successfully, a new subflow creation
netlink event is generated correctly, but the current code wrongly
avoid initializing a couple of subflow data.

The above will cause misbehavior on a few exceptional events: unneeded
mptcp-level retransmission on msk-level sequence wrap-around and infinite
mapping fallback even when a MPJ socket is present.

Address the issue factoring out the needed initialization in a new helper
and invoking the latter from __mptcp_finish_join() time for passive
subflow and from mptcp_finish_join() for active ones.

Fixes: 0530020a7c8f ("mptcp: track and update contiguous data status")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index af54a87..67311e7 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -825,6 +825,13 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk)
        mptcp_data_unlock(sk);
 }
 
+static void mptcp_subflow_joined(struct mptcp_sock *msk, struct sock *ssk)
+{
+       mptcp_subflow_ctx(ssk)->map_seq = READ_ONCE(msk->ack_seq);
+       WRITE_ONCE(msk->allow_infinite_fallback, false);
+       mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC);
+}
+
 static bool __mptcp_finish_join(struct mptcp_sock *msk, struct sock *ssk)
 {
        struct sock *sk = (struct sock *)msk;
@@ -839,6 +846,7 @@ static bool __mptcp_finish_join(struct mptcp_sock *msk, struct sock *ssk)
                mptcp_sock_graft(ssk, sk->sk_socket);
 
        mptcp_sockopt_sync_locked(msk, ssk);
+       mptcp_subflow_joined(msk, ssk);
        return true;
 }
 
@@ -3485,14 +3493,16 @@ bool mptcp_finish_join(struct sock *ssk)
                return false;
        }
 
-       if (!list_empty(&subflow->node))
-               goto out;
+       /* active subflow, already present inside the conn_list */
+       if (!list_empty(&subflow->node)) {
+               mptcp_subflow_joined(msk, ssk);
+               return true;
+       }
 
        if (!mptcp_pm_allow_new_subflow(msk))
                goto err_prohibited;
 
-       /* active connections are already on conn_list.
-        * If we can't acquire msk socket lock here, let the release callback
+       /* If we can't acquire msk socket lock here, let the release callback
         * handle it
         */
        mptcp_data_lock(parent);
@@ -3515,11 +3525,6 @@ err_prohibited:
                return false;
        }
 
-       subflow->map_seq = READ_ONCE(msk->ack_seq);
-       WRITE_ONCE(msk->allow_infinite_fallback, false);
-
-out:
-       mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC);
        return true;
 }